Electrolytic condenser



Oct. 24, 1939- A. F. P. J. CLAASSEN ET AL 2,177,013

ELECTROLYTIC CONDENSER .Filed 001:. 23, 1936 Patented Oct. 24, 19 39 2Claims.

This invention relates to wet electrolytic condensers, and moreparticularly to electrodes for 350 volts and more.

Such condensers usually have a container of conductive material actingas the cathode, and an anode whose surface area is made as large aspossible to obtain a maximum capacity for a given size container; thissurface area, which is 4 provided with an insulating oxide-coatingdielectric, determining the capacity of .the condenser. To provide thelarge surface area 'the anode is formed in various manner, for instanceas a heIically-wound aluminium strip apertured .v at various points topermit free passage of the electrolyte, or as a plate of film-formingmaterial however, have the serious drawback that the pathscathode-container are different for different points of the anode, whichresults in the series resistance of the entire condenser being extremelyunfavorable. v Although in the so-called dry electrolytic confabric.absorbing a pasty electrolyte the paths are the same, such condensershave several disthe oxide film is self-healing to only a very limitedextent, and thus after a breakdown the short circuit between theelectrodes will remain.

an electrolytic condenser with a meander-shaped anode surrounded by acathode-container equidistantly spaced therefrom, such a construction ismechanically weak and thus subject to variations in series-resistance.Moreover the great danger of short circuit between anode and cathodecontainer as a consequence of the weak construction exists. Althoughthis can be eliminated number of pointsgsuch a construction is verycomplicated, expensive and unsuitable for massproduction.

One object of the present invention is' to eliminate theabovedifliculties and to provide a wet electrolytic condenser which isof simple construction, of large capacity for a given volume, and of lowinternal resistance.

Another object is .to provide a large surfacearea electrode which can beinexpensively producedin" mass production.

In accordance with thednvention, at least one of the electrodes isformed as a plate having a bent in the shape of a star. Suchconstructions,

- from the anode through the, electrolyte to the densers having stripelectrodes separated by advantages over wet condensers, including thatWhile it has also been suggested to construct by supporting the anpdeand container at a large UNITED STATES PATENT OFFICE.

ELECTROLYTIC CONDENSER Anthonius Frederik Peter Johan Claassen, and

Cornelis de Lange, Eindhoven, Netherlands, assignors to N. V. PhilipsGloeilampenfahrieken, Eindhoven, Netherlands Application October 23,1936, Serial No. 107,290 In Germany October 26, 1935 I ingperpendicularly thereto. condensers operating on voltages of the orderof 7 By making the plate. and the rings in one piece, additionalsupporting means or means for attaching the rings to the plate areunnecessary,

by the operation of the condenser is very favor--.

able.

In another embodiment only one electrode, preferably the anode, isprovided with projecting rings, and these rings are diametricallyslotted to decrease the series-resistance.

Further advantages and features of the invention will appear as the-description progresses.

Inorder that the invention may be clearly understood and readily carriedinto effect, it will be described in more detail with reference to thaccompanying drawing, in which:

Figure l is a sectional view of a condenser having a large surfaceelectrode according to the prior art;

Fig. 2 is a sectionized side view of a condenser according to theinvention:

Fig. 3 is a sectionized side view of a condenser according to anotherembodiment of the invention;

Fig. 4 is a sectional view taken along lines H of Fig. 3. I

The disadvantages of using electrodes spaced apart at unequal distanceswill be explained'in more ,detail in connection with Fig. 1, in which ananode 3| having a star-shaped section 3|, is disposed within acylindrical cathode-container 34.

As the distances between the anode 3| and. the cathode-container 34 arenot the same throughout, the partial capacities, i. e., the capacitiesfrom which the total-capacityof the condenser fairly large, For example,consider a condenser having a total capacity of 18 mid., and anelectrolyte having a specific resistance of about 10,000 ohms per cubiccentimeter at 20 0., intended to operate on 500 volts, 50 C., andconsider another electrolyte with specific resistance of about 15,000 to20,000 ohms per 'cubic centi' meter at 20 C., intended to operate on 550volts,

.50 G. Such a condenser may have a partial capacity corresponding to 6mfd. as supplied by a surface area of about 100 square centimeters lyingat a distance of 2 cm. from the cathodewhich may readiiyoccur in theusual constructions of wet electrolytic condensers. With a specificresistance of the electrolyte of 15,000 ohms per cubic centimeter theresistance in series with the'6 mfd. will amount to 15,000 X f =aoc ohmsThis means a very high power factor loss, since the impedance of 6 mfd.at 100 cycles will amount to about 260 ohms.

Below are the calculations for a theoretical case in which the totalcapacity of the condenser is 18 mfd., (real value as would be measuredby ballistic methods) and in which the distances be- 'r m1 ca T r 1 0paco a series Frequency ity resistance Micrnfnmds Ohms 50 cycles 16.8131 100cyclcs 13.0 103 500 cycles 7.7 6%

tween the anode and cathode of the parallelconnected partial capacities"have such values that the partial capacities are in series with thefollowing resistances:

Partial capacities Resistances at 20 C.

Ohms 2 Microfarads 4 Microl'arads. 200 6 Microfarads. 400 6 Microiarads800 'A condenser having the above partial capacities and resistances inseries will have the following total capacities and total seriesresistances depending upon the frequency used:

large changes in the specific resistance of the electrolyte withtemperature. Although this does not apply to such an extent to aqueouselectrolytes, it ioes apply to high-voltage condensers in which anelectrolyte in a glycerol solution is preferably used.

This temperature dependency of the electrolyte is so great that at about45 C. for instance, the specific resistance of the electrolyte is V; theresistance at 20 C, Thus, when the values of Table I are calculated at45 (2., all of the series resistances will be reduced to one-quarter afollows:

With the partial resistances of Table III, the condenser would have thefollowing total capacities and total resistances at the givenfrequencies:

' Total Total Frequences capacity resistance Microfurads Ohms 50 cyclesi7. 4 30 100 cycles l7. 0 34 50') cycles 12. 2 24 Comparison of TablesII and IV clearly brings out the high temperature dependency of theseries resistance and of the capacity.

From the above it clearly appears that it is of great importance in anelectrolytic condenser to make the series-resistance between every pointof the formed electrode'and the counter-electrode as equal and as smallas possible.

In the embodiment of the invention illustrated in Fig. 2 the condensercomprises a positive electrode i, a negative electrode 9, and a liquidelectrolyte 30 for example a mixture of 200 gr. boric acid (HzBOa), 1000gr. glycerol, and cc. ammonia (N'HrOH) 10% by weight. The electrode lcomprises a plate portion 3| and a plurality of projecting concentricrings 32, and is provided with an insulating oxide coating. Theelectrodes are preferably made of a film-forming metal such as aluminum,which can be extruded into a onepiece body, and their active surfacesmay be etched to increase the capacity.

The electrode I is secured to a base 4 of insulating material, forinstance a moldable material containing synthetic resin, by' means of ametal pin 2 extending through a central bore in the plate portion 3| andbase 4. The pin 2 has a flanged upper end 33 bearing upon the uppersurface of plate 3|, whereas its lower end is riveted over the base 4with the interposition of a terminal I. The base 4 is provided with anexternally-threaded projecting portion 5 for mounting the condenser, anda gasket 3, for instance of rubber, is disposed between the base 4 andcircular corrugations on the adjacent surface of plate 3| to form aliquid-tight seal.

A cup-shaped member 34, whose closed end surface forms a dome 20provided with one or more apertures 22, has its lower edge bent over theedge of the base 4 with the interposition of gasket 3 to effect aliquid-tight seal. the member l4 by means of a ring-shaped indentation,formed by rolling, is the electrode 9, which is similar to electrode Iand is provided with a plurality of ring-shaped projections ll spaced soas to telescope with the rings 32 of electrode i.

Electrode 9 is provided with a plurality oi bores 19 to allow theelectrolyte 30 to flow into the space formed between the rings 32 andII, and with a central counterbore into which is secured the'top of aporcelain tube- It! extending with a snug fit into the space formed bythe inner ring 32. A gasket 0, for instance of rubber, is disposedbetween the top of pin 2 and the bot- Secured to.

tom of tube l0, whereas a gasket I 4 extends between member 9 and thetop inner ring 32 and partly within the spaces I5.

In assembling the condenser the member 9 with tube l0 secured thereto ispressed down so as to compress the gasket 8, which prevents theelectrolyte. from reaching the top of pin 2 and passing between pin 2and base I; thus preventing corrosion of pin 2. If pin 2 is of amaterial which does not form an oxide layer, gasket 8"-also serves toprevent short-circuiting between the electrodes through the electrolyte.The gasket [4 serves to space the electrodes I and 9 at the correctdistance and also to prevent the electrolyte contained in space l5 fromcreeping upward along tube Ill. The electrodes I and 9 are telescoped tosuch an extent that the distance between the ends of rings ll and thesurface l2 of plate 3| is substantially equal to the distance 13 betweenadjacent surfaces of rings 32 and II.

Bearing upon the top of the dome 20 and secured to member 34 by a rolledindentation at 36 is a cup-shaped cover 23 provided with a vent hole 25.Surrounding the dome 20 so as to cover the apertures 22 is a band offlexible material, for instance rubber, which in known manner serves tovent the gases developed during the operation of the condenser. It willbe noted that by forming a dome 20 on the member 34 and locating thevent holes 22 therein, these holes are located well above the surface ofthe electrolyte 30, thereby minimizing the possibility of theelectrolyte being carried out with the escaping vent gases.

To completely prevent the escape of electrolyte with the venting gases,and thus to prevent corrosion of objects mounted in the vicinity of thecondenser, the space formed between the members 23 and I6 is filled witha suitable liquid-absorbing material 23 such as sawdust, whereby onlythe gases will escape through the aperture 25.

The condenser shown in 'Figs. 3 and 4 has in general a constructionsimilar to that of Fig. 8 with the exception that only the anode isshaped according to the invention; the container itself acting as thecathode. In the construction shown in Figs. 3 and 4 the anode 5| issimilar to that of electrode I with the exception that the rings 52 areprovided with a plurality of, preferably about 10 to 15, diametr'icalslots 53 (see Fig. 4), which may be saw cuts. The slots 53 serve toreduce the series resistance and by giving them a width less than thethickness of the rings 52, the active surface and thus the'capacity ofthe electrode is increased, whereas the-series resistance retains asuitable value. An electrolytic condenser with an anode according to theinvention with five concentric rings of utmost diameter of 24 mm. and aheight of 55 mm., surface of the anode 275 square centimeters, has for320 volt a capacity of 32 mid, and a series resistance of only 10 ohms.This latter value may be reduced to 5 ohms by mounting in the center ofthe container a metal bar fixed to the container thus serving as aninner cathode-container. The series-resistance for a condenser ofsimilar electric properties but with an anode as drawn in Fig. 1 isabout 15 ohms or more.

While we have described our invention in connection with specificexamples and constructions, we do not wish to be limited thereto, butdesire the appended claims to be construed as broadly as permissible inview of the prior art.

What we claim is:

1. An electrolytic condenser comprising a liquid electrolyte, twoelectrodes each consisting of a one-piece body having a plate-shapedbottom portion and a plurality of concentric ring-shaped portionsextending perpendicularly to said bottom portion, said bodies beingarranged with the ring-shaped portions interlapping with their opposingsurfaces equidistantly spaced apart and parallel, the ring-shapedportions of one electrode alternating with the ring-shaped portions ofthe other electrode.

2. An electrolytic condenser comprising a liquid electrolyte, acontainer, an electrode having a bottom portion and a plurality ofconcentric rings extending perpendicularly to said portion, a secondelectrode having a bottom portion, and a plurality of rings extendingperpendicularly to said portion and telescoping with the rings of saidfirst electrode, means to insulate said electrodes from each other andto space said rings apart, said means comprising a member of insulatingmaterial secured to one electrode and extending within the inner ring ofthe second electrode, and

a gasket of insulating material extending around said member and betweensaid electrodes, said gasket also preventing creepage of the electrolytealong said member. ANTHONIUS FREDERIK PETER JOHAN CLAASSEN. CORNELIS n1:LANGE.

